|Principal Investigator: ||Ronald S. Harichandran|
|Research Assistant: ||M. Imad Baiyasi|
|Funding Agency: ||Michigan Department of Transportation|
|Period: ||January 1997 – June 2000|
Experiments were conducted to assess the effects of using glass and carbon FRP wraps, with fibers oriented in the hoop direction, for rehabilitating corrosion-damaged bridge columns.
The effect of wrapping on the rate of corrosion was investigated through an accelerated corrosion test. The wraps were used in two configuration: (1) with the FRP bonded to the concrete; and (2) with the FRP unbonded to the concrete. The results of the accelerated corrosion experiment indicate that wrapping reduced the corrosion depth in the reinforcing bars by 46% to 59% after 190 days of testing. Both glass and carbon wraps are equally effective in slowing down corrosion. Although unbonded wraps reduce stress concentrations in the FRP, they are less effective in reducing the corrosion rate than bonded wraps. It is postulated that this is due to the ingress of water along the unbonded FRP-concrete interface.
The durability of the repair using carbon and glass wraps was assessed using accelerated freeze-thaw testing, and no significant loss in axial load carrying capacity was observed after 300 cycles of freeze-thaw. The semi-empirical expression developed by Restrepo was found to be effective in predicting the axial load capacity of wrapped cylinders.
Corrosion probes were installed on six corrosion damaged field columns in the summer of 1999. These columns had considerable surface spalling and reinforcement was exposed at several locations. These columns are located on Lansing Road in Lansing, Michigan under the I-96 overpass (Bridge ID S09 and S10 of 23152)). Columns one through three are located on Pier 1 under the westbound overpass (S09), while columns four through six are located on Pier 1 under the eastbound overpass (S10). After superficial repairs to the column surface two columns were wrapped with two layers of carbon fiber sheets, two were wrapped with three layers of glass fiber sheets and two were left unwrapped as control columns. Column wrapping was done in July 1999. Field monitoring is ongoing.
- Baiyasi, I. M., and Harichandran, R. S. (2001). "Corrosion
and wrap strains in concrete bridge columns repaired with FRP
wraps." Proceedings, 80th Annual Meeting of the
Transportation Research Board, Washington, D.C., Paper No. 01-2609,
- Harichandran, R. S., and Baiyasi, M. I. (2000). "Repair of corrosion-damaged columns using FRP wraps." Report No. RC-1386, Michigan Department of Transportation, Lansing, Michigan.